Brad Dourif and Amanda Plummer are both superb as bonkers siblings in this Gothic and rarely staged piece from Tennessee Williams. Photo: Carol Rosegg

One of the weirdest, most unclassifiable plays of the year isn’t at a hip Tribeca venue but in Midtown, next door to “The Gazillion Bubble Show.”

The writing feels almost avant-garde at times, but the author isn’t some young hot shot from the Yale School of Drama — it’s Tennessee Williams. “The Two-Character Play,” now at New World Stages, may not be among his masterpieces, but its Gothic-grotesque vibe weaves a compelling spell.

Helping considerably is the casting of the idiosyncratic Amanda Plummer and Brad Dourif, both returning to the stage after long absences. Few can do cray-cray like these two — she in a string of high-intensity parts in the likes of “Agnes of God” and “Killer Joe,” he in everything from the stuttering Billy in “One Flew Over the Cuckoo’s Nest” to the voice of killer doll Chucky.

Their volatile combination of stylization and emotional punch is a good fit for Williams’ lyrical writing.

The playwright has been popping up a lot in New York lately, and there’s been a surge of interest in obscure pieces like “The Two-Character Play,” which Williams tinkered with for a few years after its 1967 premiere.

Gene David Kirk’s revival — born in London and recast in New York — is revelatory.

Williams drew from his relationship with his schizophrenic sister, Rose, to create siblings Clare (Plummer) and Felice (Dourif). Actors both, they’re abruptly abandoned by their company before a performance of something titled . . . “The Two-Character Play.”

“Your sister and you are insane,” the parting note says. It’s hard to disagree.

Undeterred, Clare and Felice launch into the show they were meant to put on, which is about Southern siblings who still share their family home decades after their parents’ grisly murder-suicide. Felice acts as protector to the mentally fragile Clare, even as he acknowledges that “she’s not easy to fool in spite of her condition” — something that applies to many of Williams’ troubled heroines.

One possible interpretation is that Felice and Clare aren’t actors but the shut-in siblings themselves, pretending to stage their own story. The action doesn’t take place on an unfinished set but in their own decrepit house, where they keep reinventing their past and present, editing as they go along.

In a time of cookie-cutter theater, the flamboyantly peculiar “The Two-Character Play” stands out. It’s not for everyone, but those who do like it will like it very much indeed.